1. Field of the Invention
This invention relates to an accommodation device for power-source drop that supplies voltage in a stable manner to a controller executing predetermined control functions, even when power-source voltage of the controller has dropped.
2. Related Art
A smart card reader/writer that executes predetermined controls is known. A method for supplying power to a smart card reader/writer from a vehicle-mounted battery via a cigarette lighter is disclosed in Japanese Patent Application Laid-open No. Heisei 6-60237. Additionally, a method for supplying power to a smart card reader/writer from a battery is disclosed in Japanese Patent Application Laid-open No. Showa 63-44291.
However, when the power-source line from the vehicle-mounted battery to the smart-card reader/writer is interrupted by operating the ignition key, or by switching the vehicle's engine on or off while the smart card reader/writer is processing the data on the smart card, the voltage supplied from the vehicle-mounted battery drops. Consequently, the smart-card reader/writer is unable to execute data processing. This inability to process data results in problems such as failure to write data to the smart card, or corruption of data.
Additionally, the output of the battery fluctuates according to the battery's usage history, ambient temperature, and other load-usage conditions. Thus, when the battery's output voltage drops while the smart-card reader/writer is processing smart card data, the smart-card reader/writer cannot execute data processing. A similar problem occurs in cases where the battery is inadvertently detached, or the supply of voltage is momentarily interrupted due to faulty battery contact while the smart-card reader/writer is processing smart card data.
Further, the occurrence of the above-described problems is not limited to a smart-card reader/writer.